With increasing development of personal computer, printers are widely used as peripheral devices of computers. Recently, color printers are greatly developed and are generally classified into two types: laser printers and ink jet printers. The cost of the laser printer is much more than that of the ink jet printer. Since the use of the ink jet printer provides an acceptable good printing quality and is cost-effective, the ink jet printer is relatively popular.
It is well known that the structure and operation of an ink cartridge are very important for determining printing quality of an ink jet printer. FIG. 1 is an exploded view illustrating a structure of a conventional ink cartridge. The ink cartridge principally comprises a main body 11, a bottom cover plate 12 and a top cover plate 13. Take a tri-color ink cartridge for example. The main body 11 comprises three ink chambers 111, 112, 113 from left to right so as to accommodate different colors of inks such as red, yellow and blue ink. The bottom cover plate 12 along with a bottom surface 114 of the main body 11 will define corresponding channels for guiding the inks to flow out, as will be illustrated in FIG. 2 in more greater details. The top cover plate 13 is attached to a top surface of the main body 11 for sealing the inks contained in the ink chambers. Generally, the main body 11, the bottom cover plate 12 and the top cover plate 13 are separately molded. Then, the bottom cover plate 12 and the top cover plate 13 are boned to the bottom surface and top surface of the main body 11, respectively, by using an ultrasonic welding technology.
FIG. 2 is a bottom view illustrating the bottom surface 114 of the ink cartridge main body 11. There are exit ports 1110, 1120 and 1130 at the base of each ink chambers 111, 112 and 113, respectively. The bottom surface 114 has some protruding structures such as channel plates, strips and edge ribs. The channel plates 1141, 1142 and 1143 extend from the exit ports 1110, 1120 and 1130, respectively, to an exit region 1144. The strips 1145 are located in the peripheries of the channel plates 1141, 1142 and 1143, and thus recesses 1146 are formed between the strips 1145 and each channel plate. The edge ribs 1147 are located at edge surfaces of the bottom surface 114.
FIG. 3 is a top view illustrating the bottom cover plate 12. The bottom cover plate 12 has rising strips 121 corresponding to recesses 1146 formed on the bottom surface 114 of the ink cartridge main body 11. The rising strips 121 are fitted into the recesses 1146 when the bottom cover plate 12 is engaged with the bottom surface 114 of the main body 11. The bottom cover plate 12 will be boned into the bottom surface 114 of the main body 11 by using an ultrasonic welding technology so as to form three channels (not shown) between the channel plates 1141, 1142 and 1143 and the rising strips 121, respectively. In such way, the inks contained in the ink chambers could flow through these channels into the exit region 1144, and then injected by a nozzle (not shown).
The ultrasonic welding technology is widely used to weld plastic materials. Such technology is performed by utilizing an ultrasonic frequency, e.g. 20 KHz, to vibrate two plastic articles on their contact areas. Then, the molecules on the contact areas are heated due to the vibration of molecules. When the temperature reaches the melting point of the plastic articles, the vibration will be stopped and thus the heated contact areas cool down. Meanwhile, these two plastic articles are welded together. By using the ultrasonic welding technology to weld the bottom cover plate 12 onto the bottom surface 114 of main body 11, a so-called stress-whitening phenomenon occurs. The stress-whitening phenomenon leads to some fractures on the contact areas, and thus results in ink leakages. In addition, some fibers and/or particulates might be generated on the contact areas, which readily blocks discharge of the inks. It is known that the above disadvantages also occur when the top cover plate 13 is welded onto the top surface of the main body 11. Furthermore, due to arrangement of the exit ports 1110, 1120 and 1130, the total length of the channels is very long and results in high friction as the inks flow therethrough. Such relatively long channel length also leads to an inferior molding evenness and an increase of welding variance.